1. Field of the Invention
The present invention relates to a method and apparatus for inserting a weft into a shed of a jet loom.
2. Description of the Prior Arts
The weft insertion of a weft into a shed is hereinafter referred to as "filling".
In the known jet loom such as the loom disclosed in U.S. Pat. No. 3,672,406, a compressed fluid is jetted from a main fluid jetting nozzle disposed on a side portion of the machine frame, and a weft is caused to fly through a guide passage formed on a sley at the time of each filling operation. The timing of the jetting of the fluid is adjusted by a transfer valve connected to a compressed fluid supply source disposed independently from the main nozzle for jetting the fluid. When a flow passage is opened by the transfer valve at the time of filling, the pressure in the main nozzle is elevated to a predetermined level after a cetain time lag and the fluid is jetted for a time necessary for filling. After passage of the time necessary for filling, the flow passage is shut by the transfer valve and, therefore, supply of the fluid from the compressed fluid supply source is stopped. However, since the main nozzle is provided with a narrowed passage, the reduction of the fluid pressure of the compressed fluid present between the transfer valve and the main nozzle is delayed and a relatively long time passes before the jetting of the fluid from the main nozzle is actually stopped. Therefore, the fluid is jetted from the main nozzle for a certain time even after completion of the filling operation, and hence, a high pressure is imposed on a weft stopped by an action of a control device and back twists are imparted to the weft. As a result, a defect of weft breakage is caused.